Fire sprinkler systems commonly include water flow sensors which are intended to provide some information about the activation of sprinkler heads within the system. The water flow sensors that are currently used throughout the industry are mechanical devices which contain a moving paddle (located within the pipe) and a microswitch. If water begins to flow within the pipe, the water flow displaces the paddle, which activates the microswitch, sending a signal to the building control panel.
The mechanical sensors currently used are difficult to install, since they are large, and must be inserted from the top side of the pipe (which is not always accessible) in order to reduce clogging of the moving paddle from sediment in the water. In addition, the mechanical flow sensors must be installed in the proper direction with respect to the direction of water flow, since the microswitch used to trigger the device can only operate in one direction. The mechanical sensors can also operate only when there is a full flow of water in the pipe, and cannot detect lower water flow rates which may indicate leaks within the system. Further, the paddles sometimes break and impede water flow. In addition, the mechanical sensors used are very costly.